Propellers or the like having variable-pitch blades



Aug. 28, 1962 E. c. HATCHER 3,051,248

PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES 1 v e e h S t e e h S 6 mm a F (k s 9 s E Q 8 3 20 l a 1 Q 1 mm. w l r m d e l 1 F \T 55 111111 1 414] MW \\:N \L J 3 km W l Q @Q 9 a m E p Q Q Aug. 28, 1962 E. c. HATCHER 3,051,248

PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES Filed April 11, 1958 6 Sheets-Sheet 2 Aug. 28, 1962 E. c. HATCHER 3,051,248

PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES 6 Sheets-Sheet 3 Filed April 11, 1958 NIH Aug. 28, 1962 E. c. HATCHER 3,051,248

PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES 6 Sheets-Sheet 4 Filed April 11 1958 Aug. 28, 1962 E. c. HATCHER PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES 6 Sheets-Sheet 5 Filed April 11, 1958 Aug. 28, 1962 E. c. HATCHER 3,051,248

PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES 6 Sheets-Sheet 6 Filed April 11, 1958 3,951,248 Patented Aug. 28, 1962 3,051,248 PROPELLERS OR THE LIKE HAVING VARIABLE-PITCH BLADES Ernest Charles Hatcher, lnstow, Woodside Road, Northwood, England Filed Apr. 11, 1958, Ser. No. 727,831 Claims priority, application Great Britain Apr. 18, 1957 2 Claims. (Cl. 170-16032) This invention concerns improvements relating to propellers or the like having variable-pitch blades. It is especially concerned with marine propellers, but is applicable also to propellers for aircraft and to bladed wheels or runners of other devices having variable pitch blades, such as pumps and water or other turbines. The invention has for its object to provide blade-displacing or adjusting means afiording economy of space and weight in the hub of the propeller or other device and achieving simplicity in production.

A marine propeller has previously been proposed in which two hydraulic servo motors are provided in the hub, one fore and one aft of the blades, and each consisting of a piston operating in a cylinder, the pistons being displaceable towards and away from each other and both of them being connected to each of the blades for the purpose of turning the blades to vary their pitch.

Such an arrangement has the advantage that the total load involved in controlling the pitch is distributed between the two servomotors, thus enabling smaller motors to be used and reducing the diameter of hub necessary for a given duty, thereby increasing the efliciency of the propeller. However, since one of the motors has to be accommodated between the blades and the propeller shaft, the blades have to be further aft than in the case of a single motor, so that for a given weight of hub a greater bending moment is imposed on the shaft.

The present invention aims at avoiding the above-mentioned disadvantage and to this end a servomotor for adjusting the pitch of the blades comprises a movable cylinder operatively connected to each of the blades and a piston movable in the cylinder and operatively connected to each of the blades, the load for controlling the pitch being shared between the piston and the cylinder. This arrangement has the advantage that the single servomotor can be located aft of the blades of a marine propeller. This improves the weight distribution and reduces the bending moment on the propeller shaft, while retaining the advantage of distributing the total load between two power-transmitting members, namely the piston and the cylinder.

Embodiments of the invention as applied to marine propellers will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a longitudinal section through the hub of a four-bladed marine propeller embodying the invention.

FIGURE 2 is a cross section (with certain parts omitted) through the said hub.

FIGURE 3 is a diagram showing the hydraulic pitch control means.

FIGURE 4 is a plan view of a detail.

FIGURE 5 is a plan view of the root of a blade.

FIGURE 6 is a View similar to FIGURE 1 of a second embodiment of the invention, and

FIGURES 7 and 8 are a longitudinal section and a cross section to a larger scale of pitch-control means for use with the arrangement of FIGURE 6.

Referring to FIGURES 1 to 5 of the drawings, 1 indicates the hub generally and 2 the roots of the propeller blades bolted at 3 to discs 4 rotatable in bearings 5 secured to the hub 1. Each disc 4 carries two crank pins 6 having tapered portions 7 of enlarged diameter fitted tightly in correspondingly tapered sockets in the disc (in FIGURES l and 2, these pins and other associated parts have been shown, for the sake of simple illustration, as though they were in the plane of section). Of the two pins 6 on each disc 4, one is connected to a cross-head 8 on the piston rod 9 of a piston 10 and the other is connected to a cross-head 11 carried by an extension 12 of a floating cylinder 13 slidable in a space 14 in the hub 1. Each pin 6 engages in a corresponding socket in a block 15 slidable in a transverse guide 16 in the corresponding cross-head as can be seen from 'FIG- URE 4.

Extending axially through the piston rod 9 and rigid therewith is a tube 17 which also extends throughout the length of the hollow propeller shaft 18 and passes through sealing bushes 19, 20 at opposite ends thereof. Oil under pressure is admitted to an annular space 21 surrounding the tube 17 or to the interior of the tube by way of ports 23, 24 under the control of a reversing valve 22 (FIGURE 3). The port 23 communicates directly with the annular space 21 and the port 24 communicates with the tube 17 through an oil box 25 and ports 26 in a coupling 27 in which the end of the tube 17 is journalled so that it can rotate with the propeller. The oil passes into the tube 17 through a bore 28 in an end plug 29. The tube 17 communicates, through ports 17a in a tube 17b constituting an extension of the tube 17 and a port 31 in the piston rod 9, with the forward space Y between the piston 10 and a diaphragm portion 12a, closing the cylinder 13, of the extension 12. The annular space 21 is connected to the aft space X between the piston 10 and the head of the cylinder 13 through ducts 31 in a flange 32 on the propeller shaft 18 and through pipes 33 which communicate with an annular space 34 surrounding a boss 35 on the cylinder, in which boss the end of the piston rod 9 slides. The annular space 34 communicates with the cylinder space X through a port 36 and passage 37 in the boss.

The reversing valve 22 (FIGURE 3) is operated by a control lever 38 connected by a link 39 to a lever 40. One end of the lever 40 is connected by a link 41 to the valve 22 and the other through a link 42 and the coupling 27 to the tube 17. The link 42 serves as a feedback device which centralises the valve 22 in a predetermined position after the relative positions of the piston 10 and floating cylinder 13 for establishing a required pitch of the blades have been established by adjustment of the control lever 38. Thereafter any tendency for the estab lished pitch to change will transmit a signal to the lever 40 by axial movement of the tube 17. Such movement will cause the lever 40 to rock about its pivot 43, so operating the valve 22 to correct the pitch-varying tendency. The floating lever 40 thus acts as a difierential device.

Operation of the valve 22 by the lever 38 connects either the cylinder space X or the cylinder space Y to the supply of oil under pressure and at the same time vents the other side of the piston to a reservoir 44 (FIG- URE 3) through a line 45 or a line 46. High-pressure oil is supphed to the valve 22 through a line 47 from a constant-delivery pump 48 which may conveniently be of vane or other positive-displacement type. When the delivery from the pump 48 is not required, it is diverted through a by-pass valve 49 and a line 50 to the reservoir 44. A gravity tank '51 is connected to the hydraulic sys tem through a line 52 and a non-return valve 53. The gravity tank 51 serves to maintain a head of oil within the system when the propeller shaft is stationary and the pump 48 is not driven.

As shown in FIGURE 1, a valve '54 in the flange 32 closes a port 55 leading to one pipe 33 under the inward loading of a spring 56 when the propeller is not rotating. However, a bore '57 then connects the hub space Z throu an annular valve channel 58 and radial ports 59 with a central bore 60 to open to the duct 31. The space Z is thus maintained full of oil, at a head determined by the gravity tank '51, when the pump is not operating, thereby preventing water from entering the hydraulic system.

-When the pump 48 is started up, pressure of oil in the duct 31 will force the valve 54 outwardly, so bringing an annular valve channel 61 into register with the port 55 and putting the bore 60 into communication with the port 55 through radial openings 62. At the same time, an annular valve channel 63 is moved into communication with the port 57. This channel 63 communicates with the bore 60 through radial openings 65 which are normally closed by a spring band 65 located in an annular recess in the valve. This band 65' will be forced away from the ports of the radial openings 65 if the pressure of oil within the hub space Z exceeds that in the duct 31, so preventing any excessive rise of pressure within the hub. The valve 54 will also be held in the outward position under centrifugal force during rotation of the propeller. To prevent excessive rise of pressure within the hub space Z when there is high pressure in the ducts 31, a non-return valve 66 may also be provided in the wall 12a of the cylinder 13.

From the foregoing description it will be seen that the forces required for controlling the pitch of the blades are contained within the piston and cylinder, so that the hub is subjected only to external loads arising from centrifugal force and thrust.

The above-described arrangement can also be used with two, three or more than four blades. In the case of a three-bladed propeller, an equal distribution of the pitch control load can be obtained by mounting the cross-head 8 on a spherical bearing surface on the piston rod 9 and providing the pins 6 with spherical ends which engage in spherical sockets in the sliding blocks 15.

The arrangement to be described with reference to FIGURES 6 to 8 is generally similar to that of FIGURES 1-5, but has certain advantages, especially with regard to simplicity. By way of example, a three-bladed propeller is shown. In this arrangement, liquid under pressure is admitted into the cylinder space X through a port 61 communicating with the tube 17 and into the cylinder space Y through a port 62 communicating with the annular space 21 between the shaft 9 and tube 17.

To prevent the build-up of excessive pressures within the hub 1', a tube 63 extends within the tube 17 throughout the length thereof and places the interior of the huh I in direct communication with the interior of the oil box 25' from which liquid can drain to a sump through a relief or pressure-reducing valve 64, set for say lbs. p.s.i., in a valve block 65. This valve block also contains a slide valve 66 whichis loaded by spring 67 into a position in which it closes the drainage duct 68 leading to the valve 64. In this position, the valve 66 leaves free a duct 69 connected at 70 to a line from a gravity tank. This enables the interior of the hub to be maintained at a pressure determined by the gravity tank, as previously described. The valve 66, however, is also subject through a pipe 71 to the delivery pressure of the pump of the hydraulic system. When the pump is in operation, the said pressure moves the valve 66, against the spring 67, to close the duct 69 from the gravity tank and to open the drainage duct 68 leading to the valve 64. With this arrangement, the interior of the hub 1 is maintained at a desired pressure to prevent leakage of Water into the hub, such pressure being provided by the gravity tank when the pump is not operating and by the pump when it is operating. 7

Instead of or in addition to the valves 64 and 66, a centrifugally operated valve '72 may be provided at the aft end of the tube 63. This valve is spring-loaded open to allow liquid under pressure to pass from the gravity tank, through the tube 63, into the interior of the hub 1. When, however, the propeller is rotating, the valve is closed centrifugally and maintains a predetermined pressure, for example 20 to 30 lbs. p.s.i., within the hub for preventing the ingress of water, such pressure being derived in knownmanner from the high-pressure side of the pump by the effect of leakages in the hub mechanism.

The supply of liquid under pressure either to the tube 17 or to the annular space 21 is again controlled by a reversing valve 22 operated by a lever 38. In this instance, however, the floating-lever type of diiferential is replaced by a toothed-wheel differential. An arm 73 coupled to the lever 38 by the spring link 39 is fast with a sleeve 74 carrying a sector 75 meshing with a pinion 76 with which also meshes a sector 77, An arm 78 for operating the valve 22 is fast with a sleeve 79 which serves as carrier for the pinion 76. The sector 77 is carried by a lever 79 coupled through a collar 80 and cross-pin 81 with the tube 17. With this arrangement, the feedback eifect is transmitted through the tubes 17 and 63 and the parts 79 and 80 to the differential device 7577.

An arrangement employing an additional tube such as 63 and mechanical control means such as are shown in FIGURE 1 or FIGURE 6 may be used in conjunction with a simplified version of the pumping system shown in FIGURE 3, in which the admission line 47 to the reversing valve is directly connected to the delivery of the pump 48 and the return line 45 of the said valve is connected to the gravity tank 51 by Way of an unloading and relief valve which ensures a constant by-passing of liquid to the said tank and a constant flow from it, by an overflow line, to the main tank 44. The Valves 49 and 53 and the lines 46 and 50 are eliminated and the gravity line 52 is directly connected to an oil box, such as 25', and thus to the tube 63. A relief valve 64 is provided on the oil box 25, but the parts 6571 are eliminated.

In a simplified control arrangement in which the return line 45 from the valve 22 is directly connected to the gravity tank 51 and there is an overflow from the said gravity tank to the main tank 44, there need be no valves, such as 64, 66, on the oil box at all.

Other modifications can be made inthe above-de scribed arrangements:

in particular, the reversing valve may be disposed in the hub co-axially with the piston and may be operated by relative movement of a tube occupying the position of the tube 17 and serving for the supply of the oil to the said valve.

The cross heads 8, 9 may be replaced by link connections between the pins 6 and the piston 10 and cylinder 13.

Instead of a constant-delivery pump 48 and by-pass or relief valves, use may be made of a variable-delivery pump of, say, the swash-plate or eccentric-ring type. The use of a variable-delivery reversible-flow pump would also be possible. A further alternative would be jet-pipe regulator control.

Finally, if desired, provision may be made whereby, in the event of failure of the oil supply, the tube 17 can be manipulated from in-board to move the blades 2 mechanically and'hold them in any predetermined position as an emergency measure.

I claim:'

1. A propeller comprising a hub, variable-pitch blades mounted on said hub, a fluid-pressure servo-motor disposed in said hub, mechanism operatively connecting said motor to said blades for imparting pitch adjustment thereto, a hollow propeller shaft on which said hub is fast, and a fluid-pressure ,system comprising a tube passing co-axially through said shaft with an annular space between them, connection means communicating between said motor and said tube and between said motor and said annular space of said shaft, valve means for controlling the admission of pressure-fluid to and its exhaust from said motor by way of said tube and said annular space, fluid-conducting means communicating, under the control of said valve means, with said motor and also communicating with the interior of said hub, a pump for providing pressure for the fluid of said fluid system, and a gravity vessel for providing a head of fluid pressure when said pump is not operating, said pump being in communication with said gravity vessel, and both said pump and said gravity vessel being in communication with said fluid-conducting means, whereby said interior of the hub is maintained under said head of fluid pressure when said pump is not operating.

2. A propeller according to claim 1, wherein a further tube is provided passing through the first-named tube and communicating between said gravity vessel and said interior of the hub.

References Cited in the file of this patent UNITED STATES PATENTS Atteslander July 4, Willi Apr. 28, Bruce Aug. 17, Strandell et a1. Nov. 2, :Strandell et al July 17, Willi Nov. 17,

FOREIGN PATENTS Great Britain June 18, Great Britain June 3, France July 6, 

